Gas turbine engines generally include a high pressure compressor for compressing air flowing through the engine, a combustor in which fuel is mixed with the compressed air and ignited to form a high energy gas stream, and a high pressure turbine. The high pressure compressor, combustor and high pressure turbine sometimes are collectively referred to as the core engine. Such gas turbine engines also may include a low pressure compressor, or booster, for supplying compressed air, for further compression, to the high pressure compressor.
Gas turbine engines are used in many applications, including in aircraft and in ships. The desired engine operating characteristics vary, of course, from application to application. For example, in some gas turbine engine applications, it often is necessary during engine operation to selectively actuate some variable geometry component which is mounted on the engine rotor. For example, in a variable pitch fan type aircraft engine, the fan blade pitch often must be continuously adjusted to meet the flight mission requirements. Boosters with variable rotor blades also may be utilized.
Actuating a rotor blade is difficult in that the control signal for varying the blade pitch must originate from a non-rotating area of the engine and then be transferred across the boundary to the rotating components. In addition, adequate blade support is required which would sustain the blade loads and at the same time allow the blade to rotate along its radial axis. It would be desirable to provide a simple and reliable actuation system for the rotor of a gas turbine engine.